1. Field of the Invention
The present invention relates to methods of formation for a quantum dots array, and more specifically, to a method of formation for a quantum dots array using a tilted substrate.
2. Description of the Related Art
As well known to those skilled in the art, excellent quantum wires cannot be formed between materials having different lattice constants. In this case, defects such as misfit and threading dislocations are created within a thin film, which degrade crystallographic and optical properties of the thin film. For example, quantum wells or quantum wires can be rarely grown without defects by forming InAs or InP on a GaAs substrate. This is because InAs or InP layer has a lattice constant different from that of GaAs substrate. So, such inconsistency of the lattice constants allows spontaneous formation of quantum dots.
In the meantime, manufacture of quantum functional devices has very important factors, i.e. uniformity and location of quantum structures. However, in quantum structure formation techniques using conventional mask or lithographic methods, those processes are sophisticated and surface defects can frequently be generated as drawbacks. In order to overcome such disadvantages, a number of studies have been investigated on the Stranski-Krastanow (S-K) growth mode which provides a quantum structure forming method based upon the difference of lattice constants between two materials. However, this mode also has problems to be solved such as location and size-control of the quantum dots.
Accordingly, the present invention has been proposed to solve the foregoing problems and it is an object of the present invention to provide a method of forming a quantum dots array in which a structure of wirelike quantum dots with good quality is formed in materials having an inconsistency in the lattice constants using a tilted substrate.
To accomplish the object and other advantages, there is provided a method of forming a quantum dots array. The method comprises the steps of: preparing a substrate having a constant crystallographic axis and a surface tilted with respect to the crystallographic axis; forming a buffer layer on the substrate by a chemical vapor deposition, the buffer layer being made of the same material as the substrate; and growing a material layer having a lattice constant which is different from that of the substrate, wherein a partial pressure of a source gas, a thickness of the buffer layer and a thickness of the material layer are adjusted during the chemical vapor deposition of the buffer layer so that sizes of quantum dots are restricted in a direction perpendicular to a step line direction due to an atomic bonding of step binding and the sizes of the quantum dots increase in a direction parallel to the step line direction, thereby obtaining quantum wires of good quality.